For many years, industry has been concerned with designing improved heaters for articles of manufacture such as seats, mirrors, handles of furniture, automotive vehicles, or other transportation vehicles. Examples of such heaters are disclosed in U.S. Pat. Nos. 7,560,670; 7,285,748; 7,223,948; 7,202,444; 6,872,882; 6,838,647; 6,710,303; 6,686,562; 6,307,188; 6,150,642; 6,084,217; 5,451,747; 5,045,673; 4,931,627; 4,857,711; and 4,777,351 all of which are expressly incorporated herein by reference for all purposes. However, the heaters disclosed in these patents suffer from drawbacks. For example, as described, one or more of these heaters may be limited in the ability to successfully offer different heat output levels when in use; the construction may lead to noise due to passenger shifting; the construction may have installation limitations due to their shape and/or their relatively rigid structures; and/or they may be otherwise subject to damage from repeated use.
Other disadvantages faced by these heaters are that they are unable to conform to the contours of the seat. Typically, these heaters are a solid square configuration, and this configuration is not capable of conforming to the contours of a seat, especially a seat containing a user. More recently seat heaters have begun adding holes or other configurations into the center of the heater; however, these still have not addressed problems faced with adapting a heater to a seat with a bite line, trenches, channels, and other contours.
As can be appreciated, seat trenches pose substantial design challenges. Typically, the location, geometry, and/or dimensions of a trench are dictated by a seat manufacturer based upon the needs of the seat for a particular textile, functionality of the seat, trim tie-down needs, or any combination thereof. Vehicle to vehicle, trench design may vary in location, orientation, geometry, and/or dimension, depending upon the particular needs of a seat. A trench design suitable for one seat may perform unpredictably for another. It is also important to take into account that within trenches, a heater is going to be subjected to deformation, and repeated cyclical loading, both potentially affecting wear and fatigue characteristics. Further, it is often desired or necessary to employ separate, but electrically connected, heating zones on opposite sides of a trench. This poses a unique design difficulty inasmuch as electrodes for achieving the electrical communication will generally need to be able to conform substantially to the shape of the trench, and/or allow for reliable and reproducible folding and/or flexing. Accordingly, it has been identified by the present inventors that it is important to employ particular designs for heaters to make them more readily adaptable from seat to seat.
U.S. Pat. No. 7,306,283, the teachings of which is incorporated by reference herein for all purposes, illustrates one particularly attractive approach for a heater design that makes the heater attractive for trench applications. See also, U.S. Pat. No. 7,205,510 (incorporated by reference). In the interest of improving upon existing technology in this field, the present teachings provide a heater that is particularly suitable for use in seats (especially seats with trenches) of automotive vehicles, but which may be adapted for application in other transportation vehicles, or other articles of manufacture as well.
Another challenge that flexible seat heaters face is in connecting wires to the flexible carrier, a first electrically conductive layer, a second electrically conductive layer, or a combination thereof. Generally, it is difficult to attach wires to form an electrical connection because the use of high temperature fusion techniques (which may be associated with certain attractive attachment approaches) cannot be employed without damaging the carrier. Furthermore, one or more of the electrically conductive layers are very thin and provide only small amounts of material to which wires can be attached. Accordingly, it has long been the practice in the art to attach electrical lines and/or electrical conductors (e.g. wires) to heaters by mechanical fasteners (e.g. brass or copper connector), and more specifically by using riveted electrical terminal structures. In those approaches, commonly one or more hole is made in a flexible heater layer through which a fastener (e.g. a rivet) is securingly positioned. In some designs, this process can be expensive, labor intensive, part intensive (e.g. five or more parts are used), and time consuming. Typical mechanical fasteners employed include a backing plate, a male portion, two rivets, and a crimp portion, and each part must be handled and attached to the carrier so that the electrical connection can be formed. Further, for some designs, attachment structures may require complicated installation techniques. Hardware selection also tends to be constrained as a result of a finite selection of available terminal structures for riveting applications. The present teachings seek to eliminate at least some of the parts and the labor (i.e. time) associated with attachment of this type, while still providing a robust and durable attachment.
In addition, historically, heaters of the present type have been designed with electrode structures having discrete ends, to which electrical connections are made. Once the end is defined, all connections must thereafter be made at such electrode power application connection ends. This makes it difficult to design seat heaters that have widespread application across a variety of seats. Packaging needs for individual seats will vary and may not permit consistent use of such application end locations. Furthermore, the size of the wires used in conjunction with seat heaters have prohibited attachment by any other method. Currently, seat heaters typically employ an 18, 16, 14 gauge wire, or larger to provide an adequate power supply to heat the seat. Such a larger gauge wire has been used to help provide an adequate power supply to the heater so that the heater can be quickly heated. In one of its aspects, the present teachings provide an elegantly simple solution to the problems that have constrained wire selection, so that a smaller gauge wire optionally may be employed without sacrificing performance or device integrity.
Another challenge faced by seat heaters is providing a seat heater with multiple temperature settings, zones, or both where the seat heater exhibits a substantially consistent temperature profile across the heated portion. Historically, seat heaters vary the temperature setting using a combination of different methods. For example, in one method the seat heater may include resistors having different resistances so that power is reduced and/or increased (e.g. based upon which resistance path is chosen) thereby varying the temperature of the heater. Another example is a seat heater that adds or subtracts zones, rings, branches, the like, or a combination thereof, so that the temperature will increase and/or decrease accordingly. The present teachings seek to eliminate the need for additional resistors, zones, or both, and provide a more consistent temperature profile across the heated portion of the seat heater.